Your doctor will evaluate your symptoms. Flu is likely to cause fever, coughing, chills and muscle aches. Flu tends to occur during winter months.
Doctors usually assume the diagnosis is flu when you have symptoms of influenza in the winter. If your symptoms or physical examination suggest something other than the flu, your doctor may order a blood test. He or she will swab your nose and throat for influenza testing.
Your doctor may order a chest X-ray. This is likely if he or she suspects that the influenza virus has caused pneumonia or may lead to a bacterial superinfection.